In a defiant speech, peppered with anti-American rhetoric and veiled threats, Iranian President Mahmoud Ahmadinejad told world leaders at the United Nations on Saturday that his country will never give up its nuclear enrichment program.

He balked at intense pressure to avoid a crisis next week by returning to negotiations with the European Union over the nuclear program. Instead, he said Iran would seek new partners and warned that his country will not "cave in to the excessive demands of certain powers."

U.S. and European diplomats greeted the speech and comments the president made at a news conference afterward with deep disappointment, saying they fell far short of expectations. Several officials predicted they would help them win support from allies weighing whether to send Iran's nuclear case next week to the U.N. Security Council, which has the authority to impose economic sanctions.

"What I heard today makes me predict that the option of reporting Iran to the Security Council remains on the agenda," French Foreign Minister Philippe Douste-Blazy told reporters even as Ahmadinejad was still speaking at the news conference.

Douste-Blazy and his British and German counterparts hoped Ahmadinejad's speech would include a renewed commitment from Iran to suspend much of its nuclear program and return to negotiations with the European Union.

The Bush administration and its European allies have struggled all week to convince other nations that the time has come to ratchet up pressure on Iran. But key countries of influence, including Russia, China and India, have said they want the issue dealt with outside the Security Council.

Earlier, Secretary of State Condoleezza Rice told the U.N. gathering that it was time to increase pressure on the Islamic republic, which built its nuclear program in secret over 18 years.

"When diplomacy has been exhausted, the Security Council must become involved," Rice said.

Rice urged Iran to return to the European negotiations, but there was no such commitment from Ahmadinejad. Instead, the newly elected Iranian president delivered a staunchly anti-American speech, and hinted Iran could take its nuclear program in a different direction.

Iran says it plans to enrich uranium to fuel its nuclear energy program. But that same enrichment capability could produce bomb-grade uranium, and the White House and European countries want Iran to give that up.

"If some try to impose their will on the Iranian people through resorting to the language of force and threats with Iran, we will reconsider our entire approach to the nuclear issue," Ahmadinejad told the General Assembly.

"We believe we should not give up to bullying," he said later at a news conference.

Ahmadinejad took many questions from reporters but refused to answer a question from an Israeli reporter and was evasive with others.

He would not stand by his remarks earlier this week that Iran would share technology with Muslim countries. He said Iran was looking for new partners, but would not say which ones.

He sought to broaden stalled talks with the European Union on Tehran's nuclear ambitions to include states such as South Africa.

"The Islamic Republic of Iran is prepared to engage in serious partnership with private and public sectors of other countries in the implementation of uranium enrichment," Ahmadinejad said.

He refused to provide further details on how such an arrangement would work or which countries would be included.

Iran has made similar proposals in the past, leaving diplomats at the United Nations wondering what happened to Ahmadinejad's promises to offer new ideas to stave off a crisis over Iran's nuclear program.

The board of the International Atomic Energy Agency will meet in Vienna on Monday to discuss Iran's nuclear program.

Iran has maintained that the program is designed to produce nuclear energy, not weapons. U.N. inspectors have not found any evidence of a weapons program but several serious questions about the scale, scope and history of the program remain unanswered and have fueled suspicion that Iran is concealing information.

U.S. and European diplomats said they will spend the next several days going over options for the week-long meeting in Vienna. The allies will ask the IAEA board to vote on sending the issue to New York, or adopt a resolution giving Iran several weeks to accept U.N. inspections or face the Security Council.

The inspectors want access to several sites, interviews with key officials and documentation to support some of Iran's claims about the peaceful nature of the program.